Epidemiology of hereditary ataxias in Spain: hospital discharge registry and population-based mortality study.

BACKGROUND: Hereditary ataxias (HA) comprise a group of genetically heterogeneous rare diseases. As important public health problems to be monitored, this study analyses the morbimortality of HA in Spain. METHODS: Data were extracted from the national death index (1981-2008), using the International Classification of Diseases (ICD) 9th revision code 334 until 1998, and 10th revision code G11 from 1999 onwards. ICD-9 codes were then selected from the national discharge dataset (1998-2007). Age-adjusted morbidity and mortality rates were obtained by gender and 5-year period. RESULTS: Of the 610 HA deaths from 1981 to 2008, 277 corresponded to Friedreich's ataxia (45.4%) and 333 (54.6%) to other and unspecified ataxias (non-Friedreich group). Both groups showed an increase in mortality trend, which was more pronounced in males from 1985-1989 to 1990-1994. Geographical distribution of mortality revealed higher risk for males, mainly in the north of Spain. A total of 5,341 HA hospitalisations were identified from 1998 to 2007. The average annual age-adjusted hospitalisation rate was 1.19 per 100,000 population, with a rising trend. CONCLUSION: This increase in morbidity and mortality, coupled with the slight interprovincial differences, indicate that more attention should be paid to these rare diseases by public authorities and society alike.